1. Field of the Invention
The present invention relates to a fuel injection type internal combustion engine and a vehicle provided with the same.
2. Description of the Related Art
Conventionally, control has been performed to make an air-fuel ratio of an internal combustion engine a theoretical air-fuel ratio in order to purify exhaust gases with a ternary catalyst. In case of performing such control, however, there is caused a problem that even an engine capable of a stable operation in a region of high-speed rotation is liable to become unstable in a region of low-speed rotation such as idling or the like.
Engines have been expected to be capable of stably performing an operation with a theoretical air-fuel ratio even in a region of low-speed rotation. To satisfy this requirement, there has been proposed an engine in which a ratio (volume ratio) ε=Q/V of a volume Q downstream of a throttle valve in an intake passage to a stroke volume V is set on the basis of a valve overlap period (see U.S. Pat. No. 6,131,554). However, it is desirable in some cases to set specifications or the like according to a type of an engine without being restrained by constraints for a volume ratio and a valve overlap period.